The novel dark green or violet and air-sensitive 1-aza-1,3-diene titanocene complexes Cp2Ti[N(R1)CHC(R2)CH(Ph)] [R1 = t-Bu, R2 = H (7a); R1 = C6H4-4-Me, R2 = H (7b); R1 = c-C6H11, R2 = Me (7c)] were prepared by the complexation of the 1-aza-1,3-dienes 1a−c to the titanocene “Cp2Ti” generated in situ by reduction of Cp2TiCl2 with magnesium. The solid-state structure of 7c shows a bent azatitanacyclic ring with a fold angle of 130.9(4)°. A series of electron-deficient 14e 1-aza-1,3-diene titanium complexes CpTi[N(R1)CHC(Me)CH(Ph)]Cl [R1 = c-C6H11 (8a), t-Bu (8b), C6H4-2-Me (8c), C6H4-4-Me (8d)] has also been prepared by reduction of CpTiCl3 with magnesium in the presence of the 1-aza-1,3-dienes R1NCHC(Me)CH(Ph) 1c−f. These new complexes were isolated as air-sensitive brown (8a,b) or dark red (8c,d) crystals in 50−65% yield. The X-ray crystal structure of 8c revealed that the coordination geometry for the 1-aza-1,3-diene ligands has substantial σ2,π-η4-metallacyclopent-4-ene character. The 1-aza-1,3-diene complexes 8a,c,d only exhibit supine geometry as confirmed by 1H NMR spectroscopy, while 8b exists in both the conventional supine geometry and the prone geometry, which is demonstrated by quite different 1H NMR chemical shift values. Addition of 8c to 1 equiv of acetophenone gives the seven-membered metallacyclic ring system CpTi[N(C6H4-4-Me)CHC(Me)CH(Ph)C(Me)PhO] (9), whose structure has also been characterized by NMR spectral data and by X-ray diffraction analysis. In contrast to 8c, the 1-aza-1,3-diene titanocene complex Cp2Ti[N(c-C6H11)CHC(Me)CH(Ph)] (7c) does not react with acetophenone even at high temperatures.

A remarkable thermal stability and unusual structures characterize the novel titanium–alkylidene compounds 1 a and 1 b (R=iPr and cyclo‐C6H11, respectively), which were obtained from methyllithium and [█CpTi█{CH(Ph)C(Me)=█CHN(R)}Cl] complexes. In the reaction, intermediary [█CpTi█{CH(Ph)C(Me)=█CHN(R)}Me] complexes are generated, which display a nominal breaking point in the form of an α‐C–H bond and thus decompose already at room temperature to form methane and 1 a or 1 b, respectively.

The reaction of TiCl 4 (THF) 2 or ZrCl 4 (THF) 2 with Mg in the presence of 1-aza-1,3-dienes (1) has been investigated. Reduction of TiCl 4 (THF) 2 with 2 equiv of Mg in the presence of 2 equiv of (R 1 )NdCHC(R 2 )dCH(Ph) yields the first homoleptic 1-aza-1,3-diene complex, [Ti-{N(R 1 )CHdC(R 2 )CH(Ph)} 2 ] (7), but only if the 1-aza-1,3-diene is substituted by a sterically demanding group at the nitrogen atom (1b: R 1 ) C 6 H 3 -2,6-iPr 2 , R 2 ) H). X-ray crystallography indicates a σ 2 ,π coordination of the heterodienes, which are reduced to 1-azabut-2-ene-1,4-diyl dianions to form folded 1-aza-2-titanacyclopent-4-ene rings. As a byproduct, the bicyclic complex [{N(R 1 )CHdC(R 2 )CH(Ph)}Ti{N(R 1 )CHdC(R 2 )CH(Ph)CH{C(R 2 )dCH-(Ph)}N(R 1 )] (8) was isolated, which is believed to arise from CdN insertion of 1b into the Ti-C bond of the intermediate [{N(R 1 )CHdC(R 2 )CH(Ph)}TiCl 2 ], followed by the coordination of a further 1-aza-1,3-diene ligand. The analogous bicyclic zirconium complex [{N(R 1 )CHd C(R 2 )CH(Ph)}Zr{N(R 1 )CHdC(R 2 )CH(Ph)CH{C(R 2 )dCH(Ph)}N(R 1 )] (6: R 1 ) cyclo-C 6 H 11 , R 2 ) Me) is the only available product when the reduction of ZrCl 4 (THF) 2 is performed in the presence of the 1-aza-1,3-diene (cyclo-C 6 H 11 )NdCHC(Me)dCHPh (1a), which is substituted by a sterically less demanding group at the terminal nitrogen atom. Addition of 2 equiv of benzophenone to 7 affords the titanium complex [Ti{OCPh 2 CH(Ph)C(R 2 )dCHN(R 1 )} 2 ] (9). The solid-state structure of 9 shows the titanium in a distorted-tetrahedral environment, being the center of two folded oxazatitanacycloheptene rings.

Eine bemerkenswerte thermische Stabilität und ungewöhnliche Strukturen zeichnen die neuartigen, aus Methyllithium >(9)150%>und [█CpTi█{CH(Ph)C(Me)=█CHN(R)}Cl]‐Komplexen erhaltenen Titanalkylidenverbindungen 1 a und 1 b (R = iPr bzw. cyclo‐C6H11) aus. Bei der Reaktion entstehen >(9)150%>intermediär Komplexe des Typs [█CpTi█{CH(Ph)C(Me)=█CHN(R)}Me], die eine „Sollbruchstelle”︁ in Form einer α‐C‐H‐Bindung aufweisen und daher schon bei Raumtemperatur unter Bildung von Methan und 1 a bzw. 1 b zerfallen.